#include<bits/stdc++.h>
#define ll long long
#define endl '\n'

using namespace std;

int32_t main() {
    ios_base :: sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    int n;
    cin >> n;
    vector<int> a(n);
    int ans = 0;
    for (auto &k : a) {
        cin >> k;
        ans ^= k;
    }

    cout << ans << endl;

    return 0;
}